Is it possible to use lazy loading with many to many relation in hibernate?

Question

hi i have two entities User and Authority they have many to many relation:

@ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    @JoinTable(name = "user_role", joinColumns = { @JoinColumn(name = "user_id") }, inverseJoinColumns = { @JoinColumn(name = "authority_id") })
    private List<Authority> authorities = new ArrayList<Authority>(0);

when i use FetchType.LAZY and try to get the authorities in user i get the exception:

org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role

here's how i get the user object:

public UserDetails loadUserByUsername(String username)
            throws UsernameNotFoundException, DataAccessException {
        User user = userDao.findUserByEmail(username);
        if (user == null)
            throw new UsernameNotFoundException("No user with username '"
                    + username + "' found!");
        return new org.springframework.security.core.userdetails.User(
                user.getEmail(), user.getPassword(), true, true, true, true,
                setUserAuthorities(user.getAuthorities()));
    }

i am using session factory to manage my transactions and @Transactional on the dao method. so is there's any ideas or solutions for this issue ?

Bozho · Accepted Answer · 2011-10-13 19:05:46Z

1

Yes, this is one of the most common exceptions. It means your session is closed at the time you try to read your collection.

The solution is to have an option session. Or to initialize the collection before having the session closed.

Btw, don't put @Transactional in the dao layer. Ideally it should be on the service layer.

edited Oct 13, 2011 at 19:05

answered Oct 13, 2011 at 16:40

Bozho

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7 Comments

Mahmoud Saleh Over a year ago

is there is any samples for the two solutions you mentioned, and i updated my question so you can understand the case.

Bozho Over a year ago

Google for OpenSessionInView. Or make the collection eager - it's a small one, so it won't be a problem

Mahmoud Saleh Over a year ago

so OpenSessionInView will be the solution if the collection is big, right ? coz i have other many to many relation between authority and permission, and one authority will have lots of permissions so eager will be an overhead here, and it must be lazy.

Mahmoud Saleh Over a year ago

and what do you think about this tutorial: cchweblog.wordpress.com/2009/10/10/…

Mahmoud Saleh Over a year ago

can you please suggest a good tutorial or links for using OpenSessionInView ?

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